My first recommendation would be to read Amazon’s own Seller University, where you will find all the policies and procedures (of which there are very many !) before you go too much further.
Link is at the bottom of your seller homepage under Learn, and here it is.
https://sellercentral.amazon.co.uk/learn/ref=xx_su_foot_xx

You cannot really create your own policies, you have to adhere to Amazon’s policies.
Was there anything in particular you were thinking of ?